This invention relates to a rotary internal combustion engine and, in particular, to a cooling system for a stratified charge engine of the Wankel type.
In liquid cooling systems for the housing assembly of rotary internal cumbustion engines of the Wankel type, such as disclosed in the Wankel et al, U.S. Pat. No. 2,988,065, it is common practice to provide cooling flow passages in the housing, which passages extend substantially parallel to the axis of the engine mainshaft. Also commonly provided are header chambers in the housing end walls constructed and arranged to provide end-to-end interconnection of the passages and thereby provide flow of coolant through those passages. These conventional cooling systems are exemplified in the Loyd, Jr. et al, U.S. Pat. No. 3,895,889; Turner et al, U.S. Pat. No. 3,289,647; Jones, U.S. Pat. No. 3,572,984 and Bentele et al, U.S. Pat. No. 3,007,460. In these conventional cooling systems, the primary heat transfer mechanism is convection. In the systems of Turner et al, Bentele et al and Jones, the coolant flows through a series flow path, first flowing through the hotter regions of the housing, then flowing through the cooler regions downstream of the hotter regions. In Loyd, Jr. et al, for each rotor, the flow is split between two separate flow paths. One flow path directs coolant from the coolant inlet through the cooler portion of the housing. The other flow path directs coolant from the inlet through the hotter portion of the housing. In both of these types of known systems, heat transfer by convection is promoted by having the coolant pass through the hotter housing regions without having a decreased pressure due to first having passed through the cooler engine regions. However, in higher output engines, the heat fluxes can be considerably beyond the levels that can be adequately cooled by convective cooling. In such engines, the predominant cooling mechanism changes to one of nucleate boiling in the high heat flux regions of the engine. Accordingly, it would be desirable to provide a cooling system which enhances this nucleate boiling cooling mechanism.
A stratified charge rotary combustion engine, such as shown in U.S. Pat. No. 4,083,329, requires a relatively large boss in the coolant flow zone to accommodate both a pilot injection nozzle and a spark plug. This boss must be located in the highest heat flux zone of the engine, i.e., the top-dead-center (TDC) region. To cool this region of the engine, it is known to route passages therethrough, one of which is routed through the "V-crotch" area between the pilot nozzle and the spark plug, as shown in U.S. Pat. No. 4,091,789. It would be desirable to balance or equalize the coolant flow among such passages to assure adequate cooling in all portions of the TDC region.